GEOMORPHOLOGIC AND COMPOSITIONAL CONTROLS ON LATE HOLOCENE AEOLIAN REACTIVATION, WHITE RIVER BADLANDS, SOUTH DAKOTA

Aeolian sedimentation chronologies of small dune fields on the periphery of the Nebraska Sand Hills provide important information on the regional extent of drought on the Great Plains. The White River Badlands (WRB) dunes are located approximately 60 km north of the Nebraska Sand Hills, in the western section of the northern Great Plains. Low- and high-relief parabolic dunes, blowouts, and sand sheets are found on upland tables adjacent to the White River. Currently, dune surfaces are stabilized by a drought tolerant mixed grass plant community. Based on optically stimulated luminescence results, three periods of aeolian activity were identified in the dune fields that span the Late Pleistocene through the late Holocene. Low-relief parabolic dunes on the upwind sections of tables, formed during the Late Pleistocene and early Holocene, appear to have been stable for long periods. Late Holocene reactivation of the dunes, caused by Little Ice Age droughts post 700-600 years ago, occurred mostly in the downwind sections of the tables, creating high relief parabolic dunes with high concentrations of blowouts. High-relief dunes are the predominant dune type through the WRB dune fields, suggesting that the Little Ice Age droughts were regionally important events in this section of the Great Plains. Failure of upwind low-relief dunes to reactivate during the middle and late Holocene is likely due to geomorphological factors, including morphology of dunes and dune fields, and compositional factors of the near surface sediment, including grain size and soil formation. To test the hypothesis that reactivation is controlled by geomorphologic or sedimentological factors, sediment samples were collected from high- and low-relief dune surfaces of known age for comparison. In addition, high-resolution drone imagery was collected from areas with age control for analysis of geomorphologic characteristics of the table surfaces and dune forms. Results of these analyses will be presented.